Showing papers on "Sampling (signal processing) published in 1979"

Compression of the ECG by Prediction or Interpolation and Entropy Encoding

Abstract: Compression of digital electrocardiogram (ECG) signals is desirable for two reasons: economic use of storage space for data bases and reduction of the data transmission rate for compatibility with telephone lines. In a sample of 220 Frank4ead ECG's the removal of signal redundancy by second-order prediction or interpolation with subsequent entropy encoding of the respective residual errors was investigated. At the sampling rate of 200 Hz, interpolation provided a 6 dB smaller residual error variance than prediction. A near-optimal value for the interpolation coefficients is 0.5, permitting simple implementation of the algorithm and requiring a word length for arithmetic processing of only 2 bits in extent of the signal precision. For linear prediction, the effects of occasional transmission errors decay exponentially, whereas for interpolation they do not, necessitating error control in certain applications. Encoding of the interpolation errors by a Huffman code truncated to ±5 quantization levels of 30 ?V, required an average word length of 2.21 bits/sample (upper 96 percentile 3 bits/sample), resulting in data transmission rates of 1327 bits/s (1800 bits/s) for three simultaneous leads sampled at the rate of 200 Hz. Thus, compared with the original signal of 8 bit samples at 500 Hz, the average compression is 9:1. Encoding of the prediction errors required an average wordlength of 2.67 bits/sample with a 96 percentile of 5.5 bits/sample, making this method less suitable for synchronous transmission.

Automatic volume adjusting apparatus

Abstract: An automatic volume adjusting apparatus comprises a volume adjusting device connected between a sound signal source and a loudspeaker; a first rectifier circuit for generating a first signal having a D.C. level corresponding to the level of a sound signal supplied from the colume adjusting device to the loudspeaker; a microphone and a second rectifier circuit for generating a second signal having a D.C. level corresponding to the level of a composite sound constituted by the sound generated by the loudspeaker and the ambient noise; a subtraction circuit for generating a third signal having a level corresponding to the level difference between the first and second signals, i.e. the level of the ambient noise; a gate circuit for sampling the third signal at predetermined intervals; and an integrator circuit for holding the output of the gate circuit for a predetermined period of time. The output of the integrator circuit controls the volume adjusting device.

A high-speed 7 bit A/D converter

Abstract: A 7 bit two-step parallel A/D converter has been designed using a new quantizer-subtractor circuit. The small delay in the new circuit allows digital signal sampling by latching comparators. A sample and hold unit is not needed which results in a fully integrable A/D function. Analog input signals up to 5 MHz can be digitally sampled with sampling frequencies up to 50 MHz. A double layer metallization process is used to reduce the die size to 2.4/spl times/2.5 mm.

Sampled data servo positioning system

Abstract: A sampled data servo positioning system employs an actuator to move a member between a current and a target position. Incremental position feedback is provided only at sampling times. The system employs a model responsive to a velocity related input signal to produce a continually available model incremental position signal. Phase comparing means indicates phase differences between the model and sampled position signals at the sampling times. The system has two operational configurations in the first of which a source of saturation control signals is connected to the actuator to cause maximum acceleration or deceleration thereof. In this first configuration, the model is forced to track the actuator motion by means of feedforward plus feedback control. The feedforward signal represents actuator performance while the feedback signal is the position signal phase difference. In the second operational configuration, a velocity profile signal is applied to the model and the actuator is forced to track the model by means of feedforward plus feedback control. The feedback signal is again the position signal phase difference but the feedforward signal is a predetermined signal representing the desired actuator current to execute the velocity profile. The sampled data servo positioning system may be the access motion control system of a sector servo disk file.

Electromagnetic flow meter

Abstract: PURPOSE:To measure the flow rate of fluid in high accuracy by providing difference between large and small energizing currents during ordinal value period and selecting the sampling interval for detecting both signal voltages at integer magnification of commerical power frequency. CONSTITUTION:An electromagnetic flow meter oscillator 4 consists of an exciting coil 5, a fluid flowing pipe 6 and electrodes 7, 7' and flows rectangular exciting current having two ordinal values at the coil 5 by a rectangular wave energizing circuit 1 to detect the difference between the signal voltage occurred at the larger ordinal exciting current and the signal voltage occurred at the smaller ordinal exciting current by a differential amplifier 12. It provides the difference between the period of the larger ordinal value of the exciting current and the period of the smaller ordinal value of the current and selects the interval from one sampling of the current to the other sampling thereof by a pulse generator 13 to the integer magnification of the period of commerical AC power supply so as to effectively remove the effects of the noise of the commerical power frequency and of electrochemical unbalance voltage.

Scan converter for ultrasonic sector scanner

Abstract: The input data format in a single-sector or multi-sector scanner imaging system is chosen such that angulated scan lines intersect a lateral line at equal increments, and along the scan lines the echo signal is sampled at different rates whereby sampling points are along parallel raster lines. Successive scan lines are stored in adjacent columns of a row-column oriented digital memory. Echo data is read out of memory row by row at a variable rate to convert the read-out data back to sector geometry. The image is displayed in real time in a cathode ray tube.

Delay compensation - Its effect in reducing sampling errors in Fourier spectroscopy

Abstract: An approximate formula is derived for the spectrum ghosts caused by periodic drive speed variations in a Michelson interferometer. The solution represents the case of fringe-controlled sampling and is applicable when the reference fringes are delayed to compensate for the delay introduced by the electrical filter in the signal channel. Numerical results are worked out for several common low-pass filters. It is shown that the maximum relative ghost amplitude over the range of frequencies corresponding to the lower half of the filter band is typically 20 times smaller than the relative zero-to-peak velocity error, when delayed sampling is used. In the lowest quarter of the filter band it is more than 100 times smaller than the relative velocity error. These values are ten and forty times smaller, respectively, than they would be without delay compensation if the filter is a 6-pole Butterworth.

Equalizer for complex data signals

Abstract: In a data receiver (40) for a quadrature-amplitude-modulated signal s (t) having symbol interval T, which is at least equal to the Nyquist frequency. With the sampling being performed at this rate, the functions conventionally provided by individual bandpass filter (12), phase splitter (14) and equalizer (22) circuits are performed by a single transversal filter equalizer (122). Tap coefficents for the transversal filter equalizer are derived in a decision-directed manner. The tendency of the tap coefficient values to drift is suppressed by adding energy to the received signal at frequencies within the band (0-n/2T) Hz at which the received signal has negligible energy.

Design and development of a high-speed electrooptic A/D converter

Abstract: A detailed analysis of a high-speed electrooptic guided wave analog-to-digital (A/D) converter has been performed. It is concluded that the development of converters in the 4-6 bit 1-2-GS/s range should be feasible. Analyses are presented which detail the design considerations for the electrooptic modulator chip, the laser sampler, and the analog signal amplifier. A design plan is presented for a 6-bit 1-GS/s converter which utilizes an array of 6 LiTaO_3 interferometric waveguide modulators to perform the conversion and a frequency-doubled mode-locked Nd:YAG laser to perform the sampling of analog signals having 500-MHz bandwidths. Preliminary waveguide device results are also reported, including the successful demonstration of an interferometric modulator with a 17-dB (98-percent) extinction ratio.

Editing system for video apparatus

Abstract: An advertising editing system for a video apparatus including a relay for controlling the operation of the video apparatus and a detector for sampling the voltage of the video signal and a comparator for comparing the sampled voltage amplitude with a reference voltage to provide an output voltage signal upon absence of picture information in the video signal for a period of time corresponding to at least one frame to activate the relay and condition the video apparatus during the period of the commercial message.

Multichannel frequency translation of sampled waveforms by decimation and interpolation

Abstract: A system and method for frequency division demultiplexing a received broad band signal into km channels, each capable of containing a baseband signal component and comprising m descending tiers of identical channel division modules with the first tier thereof comprising a first module responsive to the received broad band signal to divide such broad band signal (at baseband) into k new channels each containing a baseband spectral component. Each module of each tier of modules is constructed to respond individually (by sampling and de-sampling techniques) to the spectral component in individual ones of the channels outputted from the immediately preceding higher order tier of modules to form k new additional channels each containing a baseband spectral component. Each baseband spectral component has an upper bandwidth limit which bears the same ratio to its sampling rate as the upper bandwidth limit of the originally received broad band signal bears to its sampling rate.

Preprocessing method and device for speech recognition device

Abstract: Signal-to-noise is enhanced by including the upper sideband of a sampled-speech signal with the original baseband signal for further signal processing. The invention features shifting both bands to form a continuum from 0 Hz to the sampling frequency. Application in a speech recognition is shown.

Sampled speech compression system

Abstract: A sampled speech compression and expansion system, for two-dimensional prssing of speech or other type of audio signal, comprises transmit/encode apparatus and receive/decode apparatus. The transmit/encode apparatus comprises a low-pass filter, adapted to receive an input signal, for passing through low-frequency analog signals. A converter is connected to the low-pass filter for converting the analog signal into a digital signal. A buffer memory, whose input is connected to the converting means, stores the digitized signals. A correlator, having inputs from the A/D converter and the buffer memory, correlates the digital signal received directly from the converter with a delayed signal from the buffer memory. An "interval-select" circuit, whose input is connected to the output of the correlator, uses the autocorrelation value as a basis for comparison with subsequent peaks in the correlation value which are greater than a specified fraction of the autocorrelation value. The interval-select circuit has an output which is connected to the buffer memory, the value of the fractional peaks and their timing being stored in the buffer memory. A transform circuit, whose input is connected to the buffer memory, performs an even discrete cosine transform (EDCT) of the stored signal. A first modulator, whose input is connected to the output of the EDCT means, differentially pulse code modulates (DPCM) its input signal. A second modulator, whose input is connected to the output of the interval select circuit, differentially pulse code modulates its input signal. A multiplexer, having an input connected to the output of the first and second modulating means, combines the two differentially pulse code modulated signals. A receiver/decoder has circuits which perform an inverse function to those of the transmitter/coder and are arranged in inverse order, from input to output, to those of the transmitter/coder.

Optical measurement system

Abstract: of the Disclosure An optical measurement system, e.g. for remote telemetering, eliminates the influences of time variations on light sources, transmission lines, photo detectors etc. A pair of light sources generates two pulse-shaped optical signals of different wavelengths. A portion of each of these signals is sent to a remote measuring location by an optical fiber. Here, a change in the state of the object being observed is converted into a variation in the quantity of light trans-mission, and the resulting optical signal is returned to the signal processing portion of the system also by an optical fiber. This varied optical signal is then converted into an electric signal by a photo detector. Other portions of the original optical signals from the light sources are converted into a second electric signal by another photo detector. The ratio between the first and second electric signals is amplified by a logarithmic amplifier, and the amplified signal is passed through a sampling circuit and a synchronous detector to find the quantity of change of the measured object.

Position control system of the discontinuous feedback type

Abstract: A position control system is disclosed for aiming a mobile rocket launcher having positionable axes in the azimuth and elevation planes. The control system has a separate control subsystem for each axis of movement, and each such subsystem includes an initial aiming signal processor providing a course positioning function and a reaiming signal processor providing a fine positioning function. The initial aiming processor receives signals representing a desired position (DP), a feedback signal representing the actual position (AP) updated at predetermined sampling intervals, and an error signal (E) representing the difference between DP and AP. From signals representing AP and E, and a constant representing the stopping time of the launcher mechanism for a given control axis, the initial aiming processor produces a predicted position signal (PP) which represents the position that the launcher will reach upon termination of the actuator drive for that axis. The signal PP is then compared with the signal representing DP and depending upon a predetermined relationship between the predicted and desired positions of the launcher an actuator control signal is generated for driving the associated actuator at either a full forward or full reverse speed, or stopping and braking the associated launcher mechanism. The reaiming processor incorporates an error averaging network and an actuator signal function generator. The former averages, over a given time interval, the magnitude and directon of the error signal E, and the latter is responsive to the time average error (AE) to generate a forward or reverse actuator drive signal for an incrementally variable duration T c , that increase or decrease with the magnitude of AE and is timed to remove any remaining error in the position of the launcher for the given control axis. The reaiming processor is reactivated after each rocket launching to reaim the launcher to correct for any disturbance to its original position caused by the firing recoil, and the correlation provided by the function generator between the average error AE and the signal duration T c is updated from time to time to compensate for varying actuator drive characteristics due to wear and environmental conditions.

Data recovery system for use with a high speed serial link between two subsystems in a data processing system

Abstract: A data recovery circuit for use in a data processing system where plural subsystems are linked by a bit serial transmission line. The data transmitted over the bit serial transmission line is in the form of a phase encoded (PE) pulse signal. The data recovery circuit includes a time delay circuit for delaying the PE pulse signal by a three-quarter bit period. The three-quarter bit period delay signal permits the generation of a control clock signal. The control clock signal is used in sampling the PE pulse signal at three-quarter bit period points in order to generate a control signal that indicates the absence or presence of a transition at the midpoint of each bit period of the PE pulse signal. The control signal is used to generate a recovered clock signal by logically combining the control signal with the PE pulse signal and a one-half bit period delayed PE pulse signal. The control signal is also used to generate a recovered data signal by clocking the control signal into two cascaded flip-flops and logically combining the outputs of the two cascaded flip-flops.

Digital recording of time compounded video signal - uses parallel-serial digital signal train fed into memory for two speed sampling

Abstract: The process uses a video recorder, in which the analogue signal is digitally encoded, time compressed and multiplexed with the sync. pulses of the video signal. The reverse operation is also included so that the analogue signal can be retrieved. The digital signal is written into stores at one sampling frequency and read-out at a higher sampling frequency to achieve the time compression. The incoming analogue signal is amplified, fed through a low pass filter and sampled. Next it is digitally encoded, and its output has a parallel form. The output is fed into parallel/serial converter shift registers. The serial form data has synchronisation pulse bits added and is fed into the two sampling frequency memory system for time compression. The output of the memory is multiplexed and mixed for recording.

Horizontal scanning rate correction apparatus

Abstract: A horizontal scanning rate correction apparatus for a cathode-ray tube, particularly of the beam index color cathode-ray tube type, includes a memory for storing correction values representing deviations of the horizontal scanning rate of the electron beam from a desired scanning rate at each of a plurality of horizontal sampling positions along each of a plurality of predetermined horizontal sampling lines which are substantially fewer in number than the horizontal lines along which scanning occurs. During display of a video signal, a selected one of the stored correction values is read out of the memory for each scanning position of the beam along a scanned one of the horizontal lines, with each read correction value, and a corresponding sampling line correction signal produced therefrom, representing the deviation at a corresponding horizontal sampling position on one of the sampling lines. A scanned line correction signal is then produced for each horizontal scanning position which is a function of the sampling line correction signal and of the vertical position of the respective scanned line, and the scanned line correction signal is applied to the beam deflection yoke or device to substantially cancel the scanning rate deviation.

Apparatus for detecting the center of a welded seam in accordance with fundamental harmonic component suppression

Abstract: An apparatus first magnitizes a base metal with an alternating flux to cross the welded seam of the base metal and the resulting leakage flux from the welded seam is detected by at least one flux search element to generate an AC signal. The fundamental harmonic component corresponding to the magnetizing signal used for the alternating magnetization is eliminated from the AC signal and the resulting signal voltage is sampled at a fixed period corresponding to the period of the magnetizing signal, thus detecting the center position of the welded seam from the result of the sampling. The apparatus comprises a magnetizing coil arranged adjacent to the base metal for the alternating magnetization thereof, at least one flux search element disposed adjacent to the base metal for leakage flux detecting purposes, means for eliminating from the detected AC output signal of the element the fundamental harmonic component corresponding to the magnetizing signal used for the alternating magnetization and a sampling circuit for sampling the output signal voltage of the eliminating means at a predetermined period, whereby the relative positional relation between the flux search element and the center of the welded seam is determined in accordance with the polarity and the amplitude value of the output voltage of the sampling circuit.

Sampled data servo positioning system and sector disk file employing same

Abstract: A sampled data servo positioning system employs an actuator (50) to move a member between a current and a target position. Incremental position feedback is provided only at sampling times. The system employs a model (60,61, 64) responsive to a velocity related input signal to produce a continually available model incremental position signal. Phase comparing means (70) indicates phase differences between the model and sampled position signals at the sampling times. The system has two operational configurations in the first of which a source of saturation control signals is connected to the actuator to cause maximum acceleration or deceleration thereof. In this first configuration, the model is forced to track the actuator motion by means of feed-forward plus feedback control. The feedforward signal represents actuator performance while the feedback signal is the position signal phase difference. In the second operational configuration, a velocity profile signal is applied to the model and the actuator is forced to track the model by means of feedfoward plus feedback control. The feedback signal is again the position signal phase difference but the feedforward signal is a predetermined signal representing the desired actuator current to execute the velocity profile. The sampled data servo positioning system may be the access motion control system of a sector servo disk file.

Burst control signal generator

Abstract: PURPOSE:To enable to watch the picture of high quality through the picture with analog signal processing again after obtaining the digital signal with fidelity stably, by providing the adder and hold circuit. CONSTITUTION:Selection pulse SP, reset pulse RP, and timing pulses TP1 to TP3 are generated from the pulse generator PG based on the reference clock signal CL1. When the duration period t of the burst signal B is ended, the hold circuits HD1 to HD3 take the hold value adding the sampling signal of the same sampled phase with the addition circuits AD1 to AD3, and even if the amplitude change of the signal B at the sampling time points C1 to C5, since the phase at each cycle of the same phase is added, the changing part of amplitude is cancelled. When the value is picked up according to the sequence of sampling with the switch circuit SW1 in the order of inputs a,b, and c, the changing part is cancelled and the phase change is averaged, establishing stable burst signal and equivalent digital signal.

Digital speech interpolation system

Abstract: A digital speech interpolation system is combined with an adaptive differential PCM (ADPCM), employing a speech detector for detecting speech signals and for discriminating voiced and unvoiced sounds. An adaptive quantization bit assignment to the speech is adopted to cope with any freeze-out condition. And further PCM speech signals with 8 KHz sampling are applied to ADPCM after shifted 250 Hz down and then converted into 6 KHz sampling frequency, thereby attaining a total gain of about 7 without degrading speech quality.

Method and apparatus for sampling frequency conversion

Abstract: PURPOSE:To ensure the conversion for an optional sampling frequency without returning to the analog signal in the system to convert the sampling frequency of the sampling signal, by carrying out the conversion through the filter which eliminates the higher harmonic wave and the noise component.

Means for deriving baud timing from an available AC signal

Abstract: Baud timing is derived from an AC signal having n half-cycles during each baud period, for use in demodulating a carrier signal bearing digital information via some predetermined variation in a characteristic of the carrier signal during each baud period, by converting the carrier signal characteristic variation to a DC signal, sampling the DC signal at the same point during each half-cycle of the AC signal, summing the samples corresponding to the same half-cycle of the AC signal within each sequence of AC signal half-cycles occurring over successive baud periods, there being n such sample totals, identifying the largest one of the n totals and sychronizing the baud timing signal to the AC half-cycle corresponding thereto.

Sampling circuit and method therefor

Abstract: A sampling circuit and method therefor including a first Josephson junctionor producing a series of sampling pulses for activating a second Josephson junction that is receptive of both the analog current signal being sampled and a bias current. The first Josephson junction is continually triggered at a fixed time relative to the repetitive analog signal to provide a series of sampling pulses and before each sampling pulse the bias level to the second Josephson junction is changed until the sum of the current from the sampling pulse, from the analog signal, and from the bias source exceeds the critical current value of the second Josephson junction causing it to switch from one voltage state to another. The value of the bias current at the point of switching is proportional to the current in the analog signal. In one embodiment, the bias current is increased in a step-like fashion for each sampling pulse from the first Josephson junction until the critical value of the second Josephson junction is reached. The resolution of the analog signal for this embodiment is 1/N if there are N samples. In another embodiment where the analog signal is known to exist between two extremes, the bias current for the first sample is initially positioned at a mid-range value between the extremes. If, at the sample time, the second Josephson junction is switched, the bias current for the next sample is reduced by 1/2. If the second Josephson junction has not switched, the bias current is increased by 1/2 for the next sample. This process continues for N samples, the resulting resolution being 1/2 N .

Terminal equipment for data-transmission network including digitally operating modem

Abstract: At a subscriber station AU communicating with a central office of a data network, a logic unit UM includes a processing subunit UE which, under the control of a microprogrammed subunit UC comprising a microinstruction memory MM and a sequencer SQ, digitally demodulates an incoming carrier and synthesizes an outgoing carrier modulated in the DPSK (differential-phase-shift keying) mode. The modulation is effected by multiplying stored bits of an outgoing signal, read out from a data memory MD, with bits representing digitized sine and cosine samples of the carrier wave obtained from a calculator AL within subunit UE, followed by conversion to analog form and filtering; demodulation is carried out in a similar manner, after conversion of analog samples of the incoming carrier to digital form, by multiplying the resulting bits with those of the calculated sine and cosine samples. The sampling instants are established by a timing signal T2 digitally synchronized with the central-office clock through a phase-locking loop including an adjustable frequency divider DP controlled by an error signal from the calculator AL, emitted when the peak-indicating derivative sample has an absolute value exceeding a predetermined threshold.

Automatic waveform equalizer

Abstract: PURPOSE:To attain effective and automatic equalization by reducing an influence of a direct-current component by removing the direct-current component by passing a reference waveform through a differentiating circuit when comparing the reference waveform with a reference signal. CONSTITUTION:An input signal is inputted from input line 2 of transversal filter 1 to tapped delay line 3 and each tap output is added by adder circuit 5 under the control of tap gain control circuit group 4 before outputted to output line 6. Part of the output signal of filter 1 is differentiated by differentiating circuit 7 and the reference waveform of comparator circuit 8 is inputted and compared with the reference voltage of reference voltage generating circuit 9 at the timing generated by timing pulse generating circuit 10. By receiving part of the output signal, circuit 10 generates clock pulses of a fixed period, which are counted only at fixed time to find the center of the reference waveform, and a string of sampling pulses are generated at positions corresponding to respective taps of filter 1 centering on the found value and then supplied to comparator circuit 8. A comparison output between the differential reference waveform and reference waveform at respective tap points are supplied to tap gain control voltage generating circuit 11 to control circuit group 4, thereby correcting waveform distortion.

Method and device for acquiring the initial phase of the clock in a synchronous data receiver

Abstract: In a synchronous data transmission system wherein data transmission is achieved by modulating a carrier wave of frequency f c at the signaling rate 1/T, a method for determining the initial phase value by which the phase of the receiver clock is to be varied during an initial synchronization operation during which a synchronization signal, the spectrum of which includes two distinct lines at frequencies f 1 =f c -1/2T and f 2 =f c +1/2T, is transmitted comprising the steps of: (a) sampling the synchronization signal fed into the receiver at the rate 1/τ which is a multiple of the signaling rate, to provide a signal x(kτ) where k=a, 1, . . . , (b) multiplying the signal X(τ) by itself to provide a signal s(kτ). (c) computing the coefficient C o , which corresponds to the frequency 1/T, of the discrete Fourier transform of signal s(kτ) from N samples thereof, the number N being determined from the resolution R=1/Nτ required to overcome the effects of the frequency components, other than the component at frequency 1/T, of signal s(kτ), and (d) computing the phase of coefficient C o that represents the initial phase value by which the phase of the receiver clock is to be varied.

Servo system of discoid recording medium recording and/or reproducing device

Abstract: PURPOSE: To perform accurate and stable servo operation by sampling and storing an error signal, branched from a servo system controlling a recording and reproducing signal converting element, synchronizing with the rotation of a recording medium and by controlling the converting element by alternating or mixing the error signal of the servo system and that from a memory circuit at a prescribed mixing ratio. CONSTITUTION: Detection output signals of photodetectors 1a and 1b are passed through differential amplifier 2 and an error signal is sent from compensating circuit 3 to variable resistor 10. The output of compensating circuit 3, on the other hand, is inputted to control, arithmetic and memory circuit 8 by way of AND converter 7 and then sampled in synchronization with the rotation of a disk and sampled values are stored. An n-rotation error signal stored in memory circuit 8 and an error signal detected at that time are mixed at a prescribed ratio by variable resistor 10, whose output is supplied to actuator 5 via driving amplifier 4. On the other hand, the MFB detection coil detects the mechanical vibration of the unit and sends its output to driving amplifier 4 by way of amplifier 12 and compensating circuit 13. Thus, stable and accurate servo operation can be performed. COPYRIGHT: (C)1981,JPO&Japio